(1) Field of the Invention
The present invention relates to a process for the preparation of a biologically active polysaccharide RON substance (hereinafter referred to as "RON substance" according to circumstance) having an excellent antitumor activity, an immunomodulating activity and a host defense activity against infectious diseases, which comprises using a microorganism having an activity of producing this biologically active polysaccharide RON substance or a processed culture broth of this microorganism, and also to a novel microorganism having an activity of producing an excellent biologically active polysaccharide RON substance.
(2) Description of the Related Art
The RON substance intended in the present invention and a process for extracting this RON substance from rice bran having already been disclosed in Japanese Patent Publication No. 62-7173 (which corresponds to U.S. Pat. No. 4,762,825).
According to this conventional process, the RON substance is extracted from rice bran and the extract is purified. Therefore, the quality of the starting material is unstable, and there are considerable dispersions of the physical properties and biological activities of the obtained substance. Moreover, the yield is low and many steps are required, and the conventional process involves the problem of long operation time and is economically disadvantageous.